Aptitude - Problems on Trains - Discussion

Hey guys Haritha was right! It's also not clear to me.

Could anyone please explain me clearly?

Hi guys but the train crosses a man who is sitting in the train but not the one who is standing simply. Also he might be sitting in middle or some where else we have to calculate the distance from which the man is sitting. Isn't it?

Hi subha... @ not like dat ma...dats in d case if d faster train crosses d slower train... But in dis case d train just crosses a man(which may be considered as a point)....

What is that 18 denoting to in 5/18?

@Rohit Saluja.

When you consider relative velocity there is no need of knowing where the man is sitting and once you find out relative velocity the method of solving the problem is same as solving the problem of 'train passing a signal post or pole' so what they have given as solution is absolutely fine.

I also agree with you @Haritha.

It is not given that, where the man is sitting.

The Slower train is 500/9.

Hi, well in this question. We need the location where the man is sitting the slower train. So that we can find the distance which the faster train has to travel to cross the man sitting in slower train.

The solution to this assumes that the man is sitting at the end of the train. So in this case, length of slower train does not matter.

But assume if the man is sitting in middle of slower train, then faster train has to travel, it's own length plus half the length of slower train.

I have cleared it in another way:

We have to calculate the length of faster train only.

The relative speed = (40-20) km/hr = 20 km/hr.

Let the length of the faster train be f.

Then, (f/20 km/hr) = 5.

20 km/hr = 20*5/18 s = 50/9 s.

(9f/50) = 5.

250/9 is the answer.